From: Stefan Israelsson Tampe <INVALID.NOREPLY@gnu.org>
To: Szavai Gyula <szgyg@ludens.elte.hu>,
Stefan Israelsson Tampe <stefan.itampe@gmail.com>,
bug-guile@gnu.org
Subject: [bug #30070] multiple returns from map
Date: Fri, 15 Jul 2011 10:45:07 +0000 [thread overview]
Message-ID: <20110715-104507.sv78157.85748@savannah.gnu.org> (raw)
In-Reply-To: <20100607-182303.sv74648.31837@savannah.gnu.org>
Follow-up Comment #1, bug #30070 (project guile):
Using srfi-1 and vanilla guile gives the same erroneous behavior.
I couldn't locate the vanilla map definition in the source code but looking at
srfi-1 revealed the problem.
Basically the map is a tail loop where the reversed list is built.
Then a reverse! is done to correct the list order. This is the root
of the problem. Just replacing reverse! with reverse fixes this bug but
introduces a slight performance issue of the order of say 20%. and a double of
amount of consing done in the algorithm.
It's possible to rewrite map using a tail pointer to get the correct behavior
without penalties.
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next prev parent reply other threads:[~2011-07-15 10:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-07 18:23 [bug #30070] multiple returns from map Szavai Gyula
2011-07-15 10:45 ` Stefan Israelsson Tampe [this message]
2011-08-12 21:03 ` Andy Wingo
2011-08-13 15:56 ` Stefan Israelsson Tampe
2011-08-14 20:03 ` Andy Wingo
2011-08-14 20:52 ` Stefan Israelsson Tampe
2011-08-17 21:29 ` Andy Wingo
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